Cast Iron Cylinder Head Repair - Cold Stitch Crack Repair

There are plenty of instances where perfectly good—and often rare—cast iron cylinder head and engine block castings are scrapped due to the presence of a hairline crack in an external surface. Often these fractures result after a freeze. Remember, water volume expands 10 percent when frozen—the jacking force can snap even a sturdy Hemi block in the blink of an eye.

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In our case, we've got a healthy 440-based Max Wedge engine that runs just fine but has developed a nasty stain running down the driver side of the block. We located the leaking area—just below the exhaust port, and decided it could be fixed. To set it straight we took it to Donald Wood and the guys at RAD Auto Machine. Repairing a block using this technique takes a while, and depending on your shop, the cost might vary substantially.

Watch as we repair the crack without welding using a technique known as cold stitching. This technique is intended for low-stress surface cracks—not high load areas like main bearing webs or moving parts like connecting rods. The best use of this repair technique is to seal leaks in low pressure (100 psi or less) wet circuits—like an automotive cooling system. Let's get started.